The togavirus family has seen quite a few changes
throughout its
history. For years it was placed within the same family as flaviviruses
based on similarities in structure, genome characteristics (ss plus
stranded RNA, non-segemented genome, approx. 11 Kb., etc), and of course
the
fact that they were both transmitted through an arthropod vector.
However, with
the advent of new sequencing techniques and technologies within molecular
biology, enough differences were found between the togaviruses and
flaviviruses that the latter were moved to a separate family. Among these
differences were that the flaviviruses contain their structural proteins
at the 5'end, as opposed to the togaviruses whose structural proteins are
found at the 3' end, the flaviviruses do not produce a sub-genomic message
as the togaviruses do, and the flavivirus viral genome is capped at the 5'
end but not polyadenylated at the 3'end as is found in togaviruses. The
flavivirus genus within the newly formed flavivirus family then fell into
the category of the group B arboviruses.

Not all of the togaviruses are transmitted
through arthropods however. The rubivirus genus is composed of only one virus: the rubella virus. Rubella has been
known to be a distinct disease since the early 1800's. For hundreds of
years rubella was seen as a common disease that just about every child
would get, somewhat like chickenpox today. Children would normally
develop a rash and a slight fever. In essence the disease was not
perceived as being too serious. That all changed in 1941, when
an ophthalmologist known as Normann Gregg discovered an astounding
amount of young children with cataracts, often accompanied by a number of
congenital defects. He also noticed that this rise in cataract frequency
came right after a large outbreak of rubella.
Further research showed that the rubella virus could be devastating to the
fetus if the mother became infected during pregnancy. These
effects came to be known as congenital rubella syndrome, which is
characterised by deafness, blindness, heart disease and possibly mental
retardation. Gregg's discovery not only shed new light on rubella itself,
but also gave rise to the idea of viruses acting as teratogens, which is a
hot topic in research today, pertaining to viruses such as cytomegalovirus
and congenital cytomegalic inclusion disease, whose symptoms range from
jaundice to mental retardation and hearing loss. The
rubella vaccine, developed in 1969 and combined with the measles and mumps
vaccines in 1972, has been crucial in the prevention of rubella in the
U.S., along
with its congenital effects.

The following are important dates in the
history of
the
Togaviridae family:

Early 1800's-Rubella is identified as a distinct
disease 1930-Western Equine Encephalitis virus is first
isolated in the United
States (1st alphavirus ever isolated)

1933-Eastern Equine Encephalitis virus is first
isolated in the United
States.

1938- Venezuelan Equine Encephalitis is
isolated.

1941-Western Equine Encephalitis epidemic is seen
in
the United
States. It affects 300,000 horses and 3,336 humans.

1941-Normann Gregg notices large number of children
with cataracts following a rubella outbreak. This and other
defects are then categorized under the congenital rubella
syndrome.

1942-Semliki Forest virus is isolated in Buliyama,
Bwamba County, Uganda.

1952-Sindbis virus is isolated in the Sindbis health
district, 40 miles north of Cairo, Egypt.

1959-Ross River virus is isolated from Aedes
vigilax
mosquitoes which were trapped at the Ross River in Australia.

1962-Rubella virus is isolated in
culture.

1963-Ross River virus, which causes epidemic
polyarthritis (mostly seen in Australia), is isolated by Doherty and
colleagues.

1964-The last major epidemic of Rubella in the
United States is seen. Approximately 20,000 infants are left with
permanent damage following in-utero rubella exposure.

1969-Rubella vaccine is licensed

1971- Last epidemic of Venezuelan equine
encephalitis is seen in horses in southern Texas.

1972- The rubella vaccine is combined with the
measles and mumps vaccines to form the Measles/Mumps/Rubella (MMR)
vaccine.